Mandrels are often employed when there is a need for shaping manufactured products. Mandrels may be configured to create cured and shaped products, for instance, cured braided composite structures, thermoplastics, resin structures or any other suitable or similar materials. Mandrels can often be configured to shape the materials into a desired shape or configuration by providing actuation on the materials (for instance, composite materials) against a rigid actuation shell or form during the curing process. The pressure exerted by a mandrel against the composite material and the actuation shell or form may allow for the formation of a predetermined shape, geometry or configuration of the finished composite material. Currently, the prior art mandrels employed in the shaping of composite materials often employ a chemical reaction within the mandrel to provide actuation pressure on the composite material against the rigid actuation shell. The chemical reaction may be achieved, for example, through a soluble expandable mandrel using silicone within the actuation shell or form, or any other suitable means of generating actuation pressure with the mandrel. However, this method presents several disadvantages. Referring to FIG. 1, several examples of shaped composite structures formed by chemically actuated mandrels are shown. The chemical reactions actuating a conventional mandrel may not be sufficient to provide uniform pressure along the interior of the actuation shell. The non-uniform pressure may result in difficulties in producing uniform thickness in the composite structure formed by a conventional mandrel (see, for instance, FIGS. 1A-C).
Chemical reactions actuating a conventional mandrel may also present problems related to precision control of the pressures exerted by the conventional mandrel. Due to the nature of the chemical reaction, the pressure applied by a conventional mandrel may be uneven and difficult to control. Where shapes of the conventional mandrels are complex and have non-uniform cross sections, it may often be difficult to provide a constant pressure along the entire length of the mandrel as the chemical reaction causes the mandrel to actuate (for example, see FIG. 1C).